safety? probably not a big concern....it will pretty much guarantee that any minor wreck will take out the front end to a far greater degree. And, a savvy insurance adjuster will deny your claim because you defeated the intent of the bumper....
Personally, if I wanted to reduce the weight, I would either look for a bumper with the aluminum insert, or I would take a hole saw and put numerous perforations thru the steel piece to remove weight that way.
Given that 30# might not even gain .03sec in a stock car, I would probably say screw it and pull the carpets and put a few chunks of Fat Mat, or similar around the floorpan, maybe in the doors, under the headliner, etc., to make the system sound better and kill resonance.
Doubt it will affect the frame rigidity very much